J. Geophys. Res. http://doi.org/jjg (2012)
Oceanic oxygen levels are highly sensitive to climate variability and change. An extensive analysis of hydrographic data suggests that dissolved oxygen levels have fallen in the upper North Atlantic Ocean over the past five decades.
Ilaria Stendardo and Nicolas Gruber of ETH Zurich, Switzerland, use data from over 300 cruises to show that oxygen levels fell in upper ocean layers across much of the North Atlantic between 1960 and 2009. They suggest that changes in ocean circulation and ventilation were largely responsible this decline — which amounted to 57 Tmol of oxygen over the 50-year period. Conversely, dissolved oxygen concentrations rose in deeper water layers by an equivalent amount. An increase in the solubility of oxygen — due to the long-term cooling of these deeper waters — appears to be responsible for this rise in oxygen.
However, the researchers suggest that future warming could reduce oxygen solubility and strengthen ocean stratification, which would lead to oxygen loss throughout the entire North Atlantic.